Occupational asthma

Occupational asthma is an important occupational respiratory disorder, both in terms of morbidity, disability and in the total number of cases. The two types of occupational asthma are classified on the basis of their temporal relationship to onset. Occupational asthma with latency reflects allergic occupational asthma and is a condition characterized by a preceding latent period of workplace exposure during which allergic sensitization to a material present at the work site occurs. It is characterized biochemically by immunologic alterations and physiologically by variable and work-related airflow limitation with the presence of both specific and nonspecific airway hyperresponsiveness. In contrast, occupational asthma without latency is an asthmatic condition that develops suddenly and without a preceding latent period, as epitomized by the reactive airways dysfunction syndrome (RADS). RADS is distinguished physiologically by chronic, persistent nonspecific airway hyperresponsiveness and usually occurs after a single brief high-level exposure to an irritant gas, vapor of fume; new information suggests that a more prolonged irritant exposure, in certain susceptible persons with a pre-existing allergic predisposition, can also lead to the initiation of new-onset asthma. The factors that may be influential in the pathogenesis of occupational asthma include: exposure characteristics, industrial factors, job attributes, geographic and climatic conditions, economic considerations and personal or host conditions, such as atopy and cigarette smoking. Preventive measures and opportunities for intervention are essential and must address plans for reducing or eliminating accidents and spills, as well as plans for engineering control methods and proper and effective local exhaust ventilation. Medical surveillance programs are the keystone for prevention and should identify persons who are at an increased risk for developing occupational asthma, as well as detecting asthma at an early stage when intervention options are likely to be successful. For sensitized workers, the best preventive option is completed removal from the work environment.